*{
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
*::after{
  box-sizing: border-box;
}
*::before{
  box-sizing: border-box;
}
#demo{
  word-break: break-all;
}
#div1{
  position: fixed;
  left: 50%;
  top: 20px;
  transform: translateX(-50%);
}
#div1::before{
  content: '';
  display: block;
  position: absolute;
  left: 50%;
  width: 100px;
  height: 100px;
  border-radius: 50%;
  transform: translateX(-50%);

}
#div1::after{
  content: '';
  display: block;
  position: absolute;
  left: 50%;
  width: 100px;
  height: 100px;
  border-radius: 50%;
  transform: translateX(-50%);

}
@media(max-width: 500px){
  #html {
    height: 50vh;
    overflow: auto;
  }
  #divwrapper{
    height: 50vh;
  }
  #div1{
    position: relative;
    top: 0;
    right: 0;
  }
}